Development of in vitro methods for toxicity assessment of workplace air contaminants

摘要

Exposure to air contaminants is significantly associated with both short-term and long-term healtheffects. However, the precise mechanisms that derive such effects are not always understood. While anextensive background database from in vivo toxicological studies have been developed, most toxicitydata is from oral and dermal chemical exposures rather than inhalation exposure. There is a need toexplore new alternative approaches to provide toxicity information particularly on this technicallydemanding area. This research explores the potential of in vitro methods for toxicity assessment ofworkplace air contaminants. A tiered approach for in vitro toxicity testing of workplace contaminantswas designed in which appropriate air sampling and exposure techniques were developed. A diversifiedbattery of in vitro assays including the MTS (tetrazolium salt, Promega), NRU (neutral red uptake,Sigma) and ATP (adenosine triphosphate, Promega) and a multiple human cell system including: A549-lung derived cells; HepG2-liver derived cells, and skin fibroblasts were used. Primarily the applicationand merits of in vitro methods for prediction of toxicity of selected workplace contaminants includingAmmonium hydroxide, Cadmium chloride, Cobalt chloride, Formaldehyde, Glutaraldehyde, Manganesechloride, Mercuric chloride, Sodium dichromate, Sulphureous acid and Zinc chloride was confirmed. Tostudy the toxicity of airborne contaminants an indirect exposure method was established using airsampling techniques followed by static and dynamic direct exposure methods by culturing cells onporous membranes to reveal representative data relating to human airborne exposures. The static methodenabled the measurement of an airborne IC50 (50% inhibitory concentration) value for selected volatileorganic compounds (VOCs) including: Xylene (IC50 = 5,350-8,200 ppm) and Toluene (IC50 = 10,500-16,600 ppm) after 1 hr exposure. By implementing the dynamic method, airborne IC50 values werecalculated for gaseous contaminants including: NO2 (IC50 = 11 ± 3.54 ppm; NRU), SO2 (IC50 = 48 ±2.83 ppm; ATP) and NH3 (IC50 = 199 ± 1.41 ppm; MTS). A higher sensitivity of in vitro methods wasobserved compared to in vivo published data. A range of in vitro bioassays in conjunction with exposuretechniques developed in this thesis may provide an advanced technology for a comprehensive riskassessment of workplace air contaminants.